High voltage pulse generation device for magnetron

ABSTRACT

A high voltage pulse generation device for magnetron is disclosed. The device is divided into a DC voltage generation part, which continuously applies a variable DC voltage at a constant value to the load, and a pulse voltage generation part, which generates a momentary high voltage pulse and supplies the same to the load. The voltage applied to the load is a superposition of the output voltages from the two devices. Further, a pulse transformer demagnetization power supply is provided. A high voltage pulse waveform is obtained by momentary resonance and the pulse transformer using a low voltage at the time of pulse generation, thereby reducing the insulation space required and the size and the weight of the device. It is also possible to adjust the peak value and pulse cycle of the DC voltage applied to the load in addition to the pulse voltage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to InternationalApplication No. PCT/KR/00328, filed on Jun. 22, 1999 under the PatentCooperation Treaty, which claims priority to Korean patent ApplicationNo. 1998/23755, filed Jun. 23, 1998.

TECHNICAL FIELD

The present invention relates to a high voltage pulse generation devicefor a magnetron. The high voltage pulse generation device comprises apower supply in which a high voltage pulse is super-positioned onto theDC voltage, wherein the magnetron is driven by generating a high voltagepulse using a pulse transformer and a resonance circuit.

BACKGROUND ART

A conventional high voltage pulse generation device is constructed insuch a manner that a high pulse is generated by switching a DC powersupply using a thyristor diode module (hereinafter TDM) and by having aresonant circuit at the TDM output.

A high voltage is applied to the TDM output because the TDM output isdirectly applied to the load via the resonant circuit. This is adisadvantage in that the cost of the device is increased due to the highvoltage rating required of all the components in the circuit.

Therefore, the present invention relates to providing a relativelyinexpensive high voltage pulse generation device by using a low voltagecircuit to generate high voltage pulses.

Further, the present invention relates to providing a high voltage pulsegeneration device having reduced insulation space requirements andreduced weight.

DISCLOSURE OF INVENTION

To overcome the defects of the prior art, the high voltage pulsegeneration device of the present invention is constructed in such amanner that a high voltage switch is placed at the primary side of atransformer, a resonant circuit is constructed from components on theprimary and secondary sides of the transformer, with a high voltagepulse being applied to the load at the secondary side of thetransformer.

More specifically, the circuit presented herein is divided into twoparts, which respectively generate different types of voltages. A firstDC voltage generation part continuously applies a variable DC voltage ata required value to the load. A second pulse voltage generation partgenerates a momentary high voltage pulse and supplies the same to theload. The voltage applied to the load is the super position of theoutput voltages of the two parts. The circuit also includes a pulsetransformer demagnetization power supply, which is constructedseparately from the pulse voltage generation part, and which resets thepulse transformer core flux after pulse generation.

A high voltage pulse generation circuit is usually constructed with aresonant circuit and a high voltage switching arrangement. However,present invention generates a high voltage pulse waveform through apulse transformer and momentary resonance by using low voltage pulsegenerator, which results in a different resonant circuit construction.Because of the low voltage components, the required insulation space isreduced thereby reducing the size and the weight of the circuit ascompared with conventional circuits. Further, when necessary, the pulsegeneration circuit can adjust the peak value, number of the pulses, andthe DC voltage applied to the load. The pulse width and other pulseparameters may be varied by adjusting the component values in the designof the circuit. Additionally, a thyristor diode module is used as asemiconductor switching element for resonance generation, whichsimplifies the control and system construction resulting inmanufacturing advantages.

The power supply for the high voltage pulse generator is a DC voltageobtained by rectification from an AC power supply. The resonant circuitis constructed by connecting a resonant inductor to the primary side ofa high frequency transformer and a resonant capacitor to the secondaryside. The resonance current begins to flow as the thyristor of the TDMcycled at the design frequency. A separate complex switching operationis not required because of the backward flow of current through thediode of the TDM from the moment that the resonance current changed.

The pulse transformer demagnetization power supply controls the residualmagnetism of the pulse transformer after a pulse generation, preventingsaturation of the pulse transformer.

To switch a high voltage, several elements must be connected in seriesbecause of the limited voltage and current rating of the elements. Inthe present invention, several TDMs are serially connected, each TDMconsisting of a thyristor and a diode connected in anti-parallel.Further, the DC base voltage applied to the load is supplied by aseparate variable DC power supply circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a high voltage pulse generation devicefor a magnetron according to the present invention.

FIG. 2 is a wave diagram of the voltage and current applied to the load,along with the input voltage and current at the time of a pulsegeneration in the circuit according to the present invention.

FIG. 3 is a circuit diagram of a different construction of a variable DCpower supply device for use in a high pulse generation device formagnetron of FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Construction and operation of the present invention are described indetail with reference to accompanying drawings as follows:

FIG. 1 is a circuit diagram of a pulse voltage generation circuit inaccordance with the present invention. Thyristor diode module (“TDM”)(1) periodically interrupts an input dc power supply (Vp1) with anon-off operation. Resonant inductor (L1), which forms a resonant circuitwith resonant capacitor (C1), is connected between TDM (1) and theprimary winding of pulse transformer (2), which transforms therelatively low input dc voltage to a high voltage. Resonant capacitor(C1) is connected in series with the secondary winding of pulsetransformer (2) and connects to the load (3). Variable dc voltage source(Vdc) is connected across load t(3) for supplying the predetermined dcvoltage to the load (3). Finally, transformer demagnetization powersupply (Vp2) is connected to pulse transformer (2) for controlling theresidual magnetic flux of the transformer after pulse generation.

FIG. 2 shows the voltage and current waveforms of the circuitillustrated in FIG. 1. With reference to FIG., 2(a), at an initialstate, resonant capacitor (C1) is charged with a voltage (Vdc) providedby the variable DC power supply. When the thyristor diode module (1)becomes conductive at t=t₀, resonance is generated at the resonantcapacitor (C1) by the power supply provided from the input through thepulse transformer. While thyristor diode module (1) is conducting, aseries resonant circuit is formed comprising resonant Inductor (L1),connected on the primary side of the pulse transformer, resonantcapacitor (C1) connected on the secondary side of the pulse transformer,and the load. At time t=t₁, the pulse voltage reaches its peak, and thecurrent flowing through the TDM is zero. The direction of the currentthen changes, and reverse current starts to flow via the diode of theTDM (1). At that time, the thyristor is turned off by the reversecurrent flow, and remains off until the current through the diodeportion of the thyristor diode module (1) returns to zero, terminatingresonance. The above process is repeated with the desired pulsefrequency.

The peak value of a pulse generated by the resonant circuit can becalculated based on the following equation: $\begin{matrix}{R_{L}\operatorname{>>}{n\quad \sqrt{\frac{L \cdot \left( {{C1} + {C2}} \right)}{{C1} \cdot {C2}}}}} & (1)\end{matrix}$

wherein, n is a ratio between the number of turns on the primary side ofthe pulse transformer to the number of turns of the secondary side; C1is the capacitance of the resonant capacitor; C2 is the loadcapacitance; and R_(L) is the load resistance.

The current flowing through the secondary winding of the hightransformer is represented by the following equation: $\begin{matrix}{I_{p} = {\frac{{nV}_{p1}}{\rho}\sin \quad \omega \quad t}} & (2)\end{matrix}$

wherein,${\omega = {{1/n}\sqrt{\frac{L \cdot \left( {{C1} + {C2}} \right)}{{C1} \cdot {C2}}}}};$

and P is the equivalent impedance of the main circuit. The voltageapplied to the load is as follows: $\begin{matrix}{V_{load} = {\frac{I_{\max}}{{C2} \cdot \omega}\left( {1 - {\cos \quad \omega \quad t}} \right)}} & (3)\end{matrix}$

The peak value of the pulse voltage is then expressed by:$\begin{matrix}{V_{p \cdot {peak}} = {2n\quad V_{p1}\frac{C1}{\left( {{C1} + {C2}} \right)}}} & (4)\end{matrix}$

In FIG. 2, at the load, the pulse voltage (V_(p)) is super-positioned atthe moment of resonance on the constant DC voltage (V_(dc)).

As compared to conventional methods of pulse generation, the pulsegeneration circuit used in the present system can be miniaturized evenfurther by reducing the insulating space of a pulse transformer (2).

FIG. 3 is a circuit diagram, according to the present invention, havinga differently constructed a variable DC power supply device at the maincircuit. The variable DC power supply device (V_(dc)) comprises phasecontrol voltage converter (6), transformer (5), rectifier (4), and apulse inflow prevention diode (D1). The voltage supplied to the load istherefore constant. The phase control voltage converter (6) controls thevoltage magnitude by phase control using a non-thyristor switch capableof non-zero current turn-off.

According to the present invention, a high voltage pulse waveform isobtained by momentary resonance using a pulse transformer and a lowvoltage from a pulse voltage generation circuit. As such, the insulationspace required may be reduced, thereby reducing the size and the weightthereof.

Additional modifications and adaptations of the invention describedherein may be made that would be obvious to one of ordinary skill in theart. It is intended that the appended claims embrace the embodiments inthe foregoing description, as well as the referenced modifications.

What is claimed is:
 1. A high voltage pulse generation device comprising: (a) a pulse transformer having a first primary side winding, a second primary side winding, and a secondary side winding; (b) a first primary side circuit comprising: (b-1) a first inductor having a first terminal connected to a first terminal of said first primary side winding; (b-2) a thyristor-diode module having a first terminal connected to a second terminal of said inductor; (b-3) a first DC power supply having a first terminal connected to a second terminal of said thyristor-diode module and having a second terminal connected to a second terminal of said first primary side winding; (c) a second primary side circuit comprising: (c-1) a secondary inductor having a first terminal connected to a first terminal of said second primary side winding; (c-2) a secondary DC power supply having a first terminal connected to a second terminal of said secondary inductor and having a second terminal connected to a second terminal of said second primary side winding; and (d) a secondary side circuit comprising: (d-1) a capacitor having a first terminal connected to a first terminal of said secondary side winding; (d-2) a load having a first terminal connected to a second terminal of said capacitor and a second terminal connected to a second terminal of said secondary side winding; (d-3) a third DC power supply connected in parallel with said load.
 2. A high voltage pulse generation device according to claim 1, wherein said third DC power supply comprises: (d-3-1) an alternating current power supply; (d-3-2) a phase control voltage converter having an input connected to said alternating current power supply; (d-3-3) a high voltage transformer having a primary side connected to an output of said phase control voltage converter; (d-3-4) a rectifier having an input connected to a secondary side of said high voltage transformer, and having a first output terminal coupled to a first terminal of said load; and (d-3-5) a diode having an anode connected to a second output terminal of said rectifier and having a cathode coupled to a second terminal of said load.
 3. A high voltage pulse generating circuit comprising: a low voltage pulse generating circuit comprising a low voltage DC power supply and a switch coupled in series with said power supply; a high frequency transformer having a primary winding and a secondary winding, the primary winding coupled to receive a pulse generated by the low voltage pulse generating circuit and the secondary winding coupled to deliver the pulse to a load; a resonant circuit comprising one or more components connected to the nary winding and one or more components coupled to the secondary winding; and a variable DC voltage source coupled to the load, wherein the variable DC voltage source further comprises: an AC power source; a phase controlled voltage coupled converter having an input coupled to said AC power source; a power supply transformer having a first winding coupled to an output of said phase controlled voltage converter; and a pulse inflow prevention diode coupled between a secondary winding of the power supply transformer and the load.
 4. A high voltage pulse generation circuit comprising: a low voltage pulse generating circuit comprising a low voltage DC power supply and a switch coupled in series with said power supply; a high frequency transformer having a primary winding and a secondary winding, the primary winding coupled to receive a pulse generated by the low voltage pulse generating circuit and the secondary winding coupled to deliver the pulse to a load; and a resonant circuit comprising one or more components connected to the primary winding and one or mote components coupled to the secondary winding; and a transformer demagnetization power supply coupled to the transformer.
 5. The high voltage pulse generating circuit of claim 4 wherein the switch comprises a thyristor diode module.
 6. The high voltage pulse generating circuit of claim 4 wherein the switch comprises a plurality of series-connected thyristor diode modules.
 7. The high voltage pulse generating circuit of claim 4 fiber comprising a variable DC voltage source coupled to the load.
 8. The high voltage pulse generating circuit of claim 7 wherein the variable DC voltage source comprises: an AC power source; a phase controlled voltage coupled converter having an input coupled to said AC power sources a power supply transformer having a first winding coupled to an output of said phase controlled voltage converter; and a pulse inflow prevention diode coupled between a secondary winding of the power supply transformer and the load.
 9. The high voltage pulse generating circuit of claim 4 wherein the low voltage DC power supply comprises an AC power supply and a rectifier.
 10. The high voltage pulse generating circuit of claim 9 wherein the resonant circuit comprises: an inductor coupled between the low voltage pulse generating circuit and the primary winding of the transformer and a capacitor coupled between the secondary winding of the transformer and the load.
 11. The high voltage pulse generating circuit of claim 10 wherein the switch comprises a thyristor diode module.
 12. The high voltage pulse generating circuit of claim 10 wherein the switch comprises a plurality of series-connected thyristor diode modules.
 13. The high voltage pulse generating circuit of claim 4 wherein the resonant circuit comprises: an inductor coupled between the low voltage pulse generating circuit and the primary winding of the transformer and a capacitor coupled between the secondary winding of the transformer and the load.
 14. The high voltage pulse generating circuit of claim 13 wherein the switch comprises a thyristor diode module.
 15. The high voltage pulse generating circuit of claim 13 wherein the switch comprises a plurality of series-connected thyristor diode modules. 